This book challenges several assumptions commonly encountered in Japanese dialectology: that the pitch-accent analysis of modern Tōkyō Japanese is an appropriate basis for describing the suprasegmental phonology of other dialects and earlier stages of Japanese; that the Kyōto-type dialects have been more conservative than dialects to their east and west; that the first split in proto-Japanese was the separation of proto-Ryūkyūan; and so on. De Boer brings together evidence from recent fieldwork, premodern texts, and other sources to establish a theory of dialect divergence that avoids the problems these assumptions entail.